Typical Application Circuits
C
Differential Amplifier
R2
The circuit shown in Figure 4 performs the difference function. If
the resistors ratios are equal ( R4 / R3 = R2 / R1 ), then
R1
VIN
V
OUT = ( Vp – Vn ) × R2 / R1 + Vref.
VOUT
SGM321
R2
R1
Vn
R3 = R1 // R2
VOUT
SGM321
Vp
R3
Figure 6. Low Pass Active Filter
R4
Vref
Figure 4. Differential Amplifier
Instrumentation Amplifier
The circuit in Figure 5 performs the same function as that in Figure 4
but with the high input impedance.
R2
R1
SGM321
Vn
SGM321
VOUT
Vp
R3
R4
SGM321
Vref
Figure 5. Instrumentation Amplifier
Low Pass Active Filter
The low pass filter shown in Figure 6 has a DC gain of ( - R2 / R1 )
and the –3dB corner frequency is 1/2πR2C. Make sure the filter is
within the bandwidth of the amplifier. The Large values of feedback
resistors can couple with parasitic capacitance and cause undesired
effects such as ringing or oscillation in high-speed amplifiers. Keep
resistors value as low as possible and consistent with output loading
consideration.
８
SGM321/358/324
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
